libflux: return routes via const in msg API

Problem: The functions flux_msg_get_route_first() and
flux_msg_get_route_last() return route IDs via an allocated string
that must be freed by the user.  This API made sense previously
when route IDs were stored internally in a zframe.  However, now
that the route IDs are stored in decoded data structures, we could
return the route IDs directly.

Solution: Return internally stored route IDs via a const char *
instead of an allocated string.  Adjust all callers accordingly.
use 'const char *' instead of 'char *' in several places where
more appropriate.

src/broker/broker.c

@@ -1079,11 +1079,10 @@ static void broker_panic_cb (flux_t *h, flux_msg_handler_t *mh,
 static void broker_disconnect_cb (flux_t *h, flux_msg_handler_t *mh,
                                const flux_msg_t *msg, void *arg)
 {
-    char *sender = NULL;
+    const char *sender;
 
     if (flux_msg_get_route_first (msg, &sender) == 0) {
         exec_terminate_subprocesses_by_uuid (h, sender);
-        free (sender);
     }
     /* no response */
 }
@@ -1092,7 +1091,7 @@ static void broker_sub_cb (flux_t *h, flux_msg_handler_t *mh,
                         const flux_msg_t *msg, void *arg)
 {
     broker_ctx_t *ctx = arg;
-    char *uuid = NULL;
+    const char *uuid;
     const char *topic;
 
     if (flux_request_unpack (msg, NULL, "{ s:s }", "topic", &topic) < 0)
@@ -1107,19 +1106,17 @@ static void broker_sub_cb (flux_t *h, flux_msg_handler_t *mh,
         goto error;
     if (flux_respond (h, msg, NULL) < 0)
         flux_log_error (h, "%s: flux_respond", __FUNCTION__);
-    free (uuid);
     return;
 error:
     if (flux_respond_error (h, msg, errno, NULL) < 0)
         flux_log_error (h, "%s: flux_respond_error", __FUNCTION__);
-    free (uuid);
 }
 
 static void broker_unsub_cb (flux_t *h, flux_msg_handler_t *mh,
                           const flux_msg_t *msg, void *arg)
 {
     broker_ctx_t *ctx = arg;
-    char *uuid = NULL;
+    const char *uuid;
     const char *topic;
 
     if (flux_request_unpack (msg, NULL, "{ s:s }", "topic", &topic) < 0)
@@ -1134,12 +1131,10 @@ static void broker_unsub_cb (flux_t *h, flux_msg_handler_t *mh,
         goto error;
     if (flux_respond (h, msg, NULL) < 0)
         flux_log_error (h, "%s: flux_respond", __FUNCTION__);
-    free (uuid);
     return;
 error:
     if (flux_respond_error (h, msg, errno, NULL) < 0)
         flux_log_error (h, "%s: flux_respond_error", __FUNCTION__);
-    free (uuid);
 }
 
 static int route_to_handle (const flux_msg_t *msg, void *arg)
@@ -1175,7 +1170,7 @@ static void service_add_cb (flux_t *h, flux_msg_handler_t *w,
 {
     broker_ctx_t *ctx = arg;
     const char *name = NULL;
-    char *sender = NULL;
+    const char *sender;
     module_t *p;
     struct flux_msg_cred cred;
 
@@ -1194,12 +1189,10 @@ static void service_add_cb (flux_t *h, flux_msg_handler_t *w,
         goto error;
     if (flux_respond (h, msg, NULL) < 0)
         flux_log_error (h, "service_add: flux_respond");
-    free (sender);
     return;
 error:
     if (flux_respond_error (h, msg, errno, NULL) < 0)
         flux_log_error (h, "service_add: flux_respond_error");
-    free (sender);
 }
 
 static void service_remove_cb (flux_t *h, flux_msg_handler_t *w,
@@ -1208,7 +1201,7 @@ static void service_remove_cb (flux_t *h, flux_msg_handler_t *w,
     broker_ctx_t *ctx = arg;
     const char *name;
     const char *uuid;
-    char *sender = NULL;
+    const char *sender;
     struct flux_msg_cred cred;
 
     if (flux_request_unpack (msg, NULL, "{ s:s }", "service", &name) < 0
@@ -1229,12 +1222,10 @@ static void service_remove_cb (flux_t *h, flux_msg_handler_t *w,
     service_remove (ctx->services, name);
     if (flux_respond (h, msg, NULL) < 0)
         flux_log_error (h, "service_remove: flux_respond");
-    free (sender);
     return;
 error:
     if (flux_respond_error (h, msg, errno, NULL) < 0)
         flux_log_error (h, "service_remove: flux_respond_error");
-    free (sender);
 }
 
 
@@ -1693,7 +1684,7 @@ static void broker_request_sendmsg (broker_ctx_t *ctx, const flux_msg_t *msg)
 static int broker_response_sendmsg (broker_ctx_t *ctx, const flux_msg_t *msg)
 {
     int rc;
-    char *uuid = NULL;
+    const char *uuid;
 
     if (flux_msg_get_route_last (msg, &uuid) < 0)
         return -1;
@@ -1705,7 +1696,6 @@ static int broker_response_sendmsg (broker_ctx_t *ctx, const flux_msg_t *msg)
         rc = overlay_sendmsg (ctx->overlay, msg, OVERLAY_DOWNSTREAM);
     else
         rc = module_response_sendmsg (ctx->modhash, msg);
-    ERRNO_SAFE_WRAP (free, uuid);
     return rc;
 }
 

src/broker/log.c

@@ -596,24 +596,20 @@ static void dmesg_request_cb (flux_t *h, flux_msg_handler_t *mh,
 
 static int cmp_sender (const flux_msg_t *msg, const char *uuid)
 {
-    char *sender = NULL;
-    int rc = 0;
+    const char *sender;
 
     if (flux_msg_get_route_first (msg, &sender) < 0)
-        goto done;
+        return 0;
     if (!sender || strcmp (sender, uuid) != 0)
-        goto done;
-    rc = 1;
-done:
-    free (sender);
-    return rc;
+        return 0;
+    return 1;
 }
 
 static void disconnect_request_cb (flux_t *h, flux_msg_handler_t *mh,
                                    const flux_msg_t *msg, void *arg)
 {
     logbuf_t *logbuf = arg;
-    char *sender = NULL;
+    const char *sender;
     const flux_msg_t *msgp;
     zlist_t *tmp = NULL;
 
@@ -635,7 +631,6 @@ static void disconnect_request_cb (flux_t *h, flux_msg_handler_t *mh,
             zlist_remove (logbuf->followers, (flux_msg_t *)msgp);
     }
 done:
-    free (sender);
     zlist_destroy (&tmp);
     /* no response */
 }

src/broker/module.c

@@ -340,26 +340,22 @@ int module_sendmsg (module_t *p, const flux_msg_t *msg)
 
 int module_response_sendmsg (modhash_t *mh, const flux_msg_t *msg)
 {
-    char *uuid = NULL;
-    int rc = -1;
+    const char *uuid;
     module_t *p;
 
     if (!msg)
         return 0;
     if (flux_msg_get_route_last (msg, &uuid) < 0)
-        goto done;
+        return -1;
     if (!uuid) {
         errno = EPROTO;
-        goto done;
+        return -1;
     }
     if (!(p = zhash_lookup (mh->zh_byuuid, uuid))) {
         errno = ENOSYS;
-        goto done;
+        return -1;
     }
-    rc = module_sendmsg (p, msg);
-done:
-    free (uuid);
-    return rc;
+    return module_sendmsg (p, msg);
 }
 
 int module_disconnect_arm (module_t *p,

src/broker/overlay.c

@@ -378,7 +378,7 @@ int overlay_sendmsg (struct overlay *ov,
     int type;
     uint8_t flags;
     flux_msg_t *cpy = NULL;
-    char *uuid = NULL;
+    const char *uuid;
     uint32_t nodeid;
     struct child *child;
     int rc;
@@ -466,13 +466,11 @@ int overlay_sendmsg (struct overlay *ov,
         default:
             goto inval;
     }
-    free (uuid);
     flux_msg_decref (cpy);
     return 0;
 inval:
     errno = EINVAL;
 error:
-    ERRNO_SAFE_WRAP (free, uuid);
     flux_msg_decref (cpy);
     return -1;
 }
@@ -567,7 +565,7 @@ static void child_cb (flux_reactor_t *r, flux_watcher_t *w,
     flux_msg_t *msg;
     int type = -1;
     const char *topic = NULL;
-    char *sender = NULL;
+    const char *sender = NULL;
     struct child *child;
     int status;
 
@@ -612,7 +610,6 @@ static void child_cb (flux_reactor_t *r, flux_watcher_t *w,
     }
     ov->recv_cb (msg, OVERLAY_DOWNSTREAM, ov->recv_arg);
 handled:
-    free (sender);
     flux_msg_decref (msg);
     return;
 drop:
@@ -623,7 +620,6 @@ static void child_cb (flux_reactor_t *r, flux_watcher_t *w,
               type != -1 ? flux_msg_typestr (type) : "message",
               topic ? topic : "-",
               sender != NULL ? sender : "unknown");
-    free (sender);
     flux_msg_decref (msg);
 }
 

src/broker/test/overlay.c

@@ -256,7 +256,7 @@ void trio (flux_t *h)
     zsock_t *zsock_none;
     zsock_t *zsock_curve;
     zcert_t *cert;
-    char *sender;
+    const char *sender;
 
     ctx[0] = ctx_create (h, "trio", size, 0, recv_cb);
 
@@ -313,7 +313,6 @@ void trio (flux_t *h)
     ok (flux_msg_get_route_first (rmsg, &sender) == 0
         && sender != NULL && !strcmp (sender, ctx[1]->uuid),
         "%s: received message sender is rank 1", ctx[0]->name);
-    free (sender);
 
     /* Send request 0->1
      * Side effect: during recvmsg_timeout(), reactor allows hello response
@@ -336,7 +335,6 @@ void trio (flux_t *h)
     ok (flux_msg_get_route_first (rmsg, &sender) == 0
         && sender != NULL && !strcmp (sender, ctx[0]->uuid),
         "%s: request sender is rank 0", ctx[1]->name);
-    free (sender);
 
     /* Response 1->0
      */

src/cmd/flux-start.c

@@ -860,14 +860,12 @@ void disconnect_cb (flux_t *h,
                     const flux_msg_t *msg,
                     void *arg)
 {
-    char *uuid = NULL;
+    const char *uuid;
 
     if (flux_msg_get_route_first (msg, &uuid) < 0)
-        goto done;
+        return;
     if (ctx.verbose >= 1)
         log_msg ("disconnect from %.5s", uuid);
-done:
-    free (uuid);
 }
 
 const struct flux_msg_handler_spec htab[] = {

src/common/libflux/handle.c

@@ -684,7 +684,7 @@ flux_msg_t *flux_recv (flux_t *h, struct flux_match match, int flags)
     cali_begin_int (h->prof.msg_match_tag, match.matchtag);
     cali_begin_string (h->prof.msg_match_glob,
                        match.topic_glob ? match.topic_glob : "NONE");
-    char *sender = NULL;
+    const char *sender = NULL;
     flux_msg_get_route_first (msg, &sender);
     if (sender)
         cali_begin_string (h->prof.msg_sender, sender);
@@ -694,8 +694,6 @@ flux_msg_t *flux_recv (flux_t *h, struct flux_match match, int flags)
     cali_end (h->prof.msg_match_type);
     cali_end (h->prof.msg_match_tag);
     cali_end (h->prof.msg_match_glob);
-
-    free (sender);
 #endif
     return msg;
 fatal:

src/common/libflux/message.c

@@ -1001,7 +1001,7 @@ int flux_msg_pop_route (flux_msg_t *msg, char **id)
 }
 
 /* replaces flux_msg_nexthop */
-int flux_msg_get_route_last (const flux_msg_t *msg, char **id)
+int flux_msg_get_route_last (const flux_msg_t *msg, const char **id)
 {
     struct route_id *r;
 
@@ -1013,10 +1013,8 @@ int flux_msg_get_route_last (const flux_msg_t *msg, char **id)
         errno = EPROTO;
         return -1;
     }
-    if ((r = list_top (&msg->routes, struct route_id, route_id_node))) {
-        if (!((*id) = strdup (r->id)))
-            return -1;
-    }
+    if ((r = list_top (&msg->routes, struct route_id, route_id_node)))
+        (*id) = r->id;
     else
         (*id) = NULL;
     return 0;
@@ -1033,7 +1031,7 @@ static int find_route_first (const flux_msg_t *msg, struct route_id **r)
 }
 
 /* replaces flux_msg_sender */
-int flux_msg_get_route_first (const flux_msg_t *msg, char **id)
+int flux_msg_get_route_first (const flux_msg_t *msg, const char **id)
 {
     struct route_id *r = NULL;
 
@@ -1043,10 +1041,8 @@ int flux_msg_get_route_first (const flux_msg_t *msg, char **id)
     }
     if (find_route_first (msg, &r) < 0)
         return -1;
-    if (r) {
-        if (!((*id) = strdup (r->id)))
-            return -1;
-    }
+    if (r)
+        (*id) = r->id;
     else
         (*id) = NULL;
     return 0;
@@ -1082,7 +1078,7 @@ static int flux_msg_get_route_size (const flux_msg_t *msg)
     return size;
 }
 
-static char *flux_msg_get_route_nth (const flux_msg_t *msg, int n)
+static const char *flux_msg_get_route_nth (const flux_msg_t *msg, int n)
 {
     struct route_id *r = NULL;
     int count = 0;
@@ -1117,7 +1113,7 @@ char *flux_msg_get_route_string (const flux_msg_t *msg)
     if (!(cp = buf = malloc (len + hops + 1)))
         return NULL;
     for (n = hops - 1; n >= 0; n--) {
-        char *id;
+        const char *id;
         if (cp > buf)
             *cp++ = '!';
         if (!(id = flux_msg_get_route_nth (msg, n))) {

src/common/libflux/message.h

@@ -330,19 +330,19 @@ int flux_msg_push_route (flux_msg_t *msg, const char *id);
  */
 int flux_msg_pop_route (flux_msg_t *msg, char **id);
 
-/* Copy the first route (e.g. first pushed route) contents (or NULL)
- * to 'id'.  Caller must free 'id'.
+/* Return the first route (e.g. first pushed route) contents (or NULL)
+ * to 'id'.
  * For requests, this is the sender; for responses, this is the recipient.
  * Returns 0 on success, -1 with errno set (e.g. EPROTO) on failure.
  */
-int flux_msg_get_route_first (const flux_msg_t *msg, char **id);
+int flux_msg_get_route_first (const flux_msg_t *msg, const char **id);
 
-/* Copy the last route (e.g. most recent pushed route) contents (or NULL)
- * to 'id'.  Caller must free 'id'.
+/* Return the last route (e.g. most recent pushed route) contents (or NULL)
+ * to 'id'.
  * For requests, this is the last hop; for responses: this is the next hop.
  * Returns 0 on success, -1 with errno set (e.g. EPROTO) on failure.
  */
-int flux_msg_get_route_last (const flux_msg_t *msg, char **id);
+int flux_msg_get_route_last (const flux_msg_t *msg, const char **id);
 
 /* Return the number of route frames in the message.
  * It is an EPROTO error if there is no route stack.